GB2208033A

GB2208033A - Electrochemical cell

Info

Publication number: GB2208033A
Application number: GB08819240A
Authority: GB
Inventors: Johan Coetzer; Johannes Petrus Muller; Anthony Ayton Meintjes; Isak Louw Vlok
Original assignee: Lilliwyte SA
Current assignee: Lilliwyte SA
Priority date: 1987-08-14
Filing date: 1988-08-12
Publication date: 1989-02-15
Anticipated expiration: 2008-08-12
Also published as: DE3827479A1; GB8719321D0; FR2620869A1; ZA885793B; GB2208033B; GB8819240D0; JPS6465777A

Description

22 0 8 0 i" -I- Blectrochemical Cell THIS INTENTION relates to a

rechargeable high temperature electrochemical power storage cell. More particularly it relates to such a cell of the type comprising a liquid anode substance and an active cathode substance in contact with a liquid electrolyte, the anode substance and liquid electrolyte being separated by a separator which is permeable to the anode substance in ionic form.

According to the invention there is provided a rechargeable high temperature electrochemical power storage cell which comprises a cell housing divided by a solid separator into a pair of electrode compartments, one of which is an anode compartment uhlci corntains an active anode substance, and the other of which is a cathode compartment which contains an active cathode substance and an electrolyte, said anode substance and said electrolyte being liquid at the operating temperature of the cell, the separator separating the anode substance from the electrolyte and cathode substance and permitting the anode substance in use to pass from the anode compartment into the cathode compartment and vice versa in ionic form, the separator being compression sealed to the housing to separate the compartments from each other; by at least one compression seal comprising, in combination, a close-wound radially resilient helical metal spring and at least one sealing strip of ductile metal, the spring providing a backing for each sealing strip and being stressed C 0 in its radial direction by a force sufficient resiliently to compress the spring in its radial direction and sufficient to cause plastic deformation of each sealing strip.

There may be two said sealing strips on opposite sides respectively of each coil spring and plastically defonpecl thereby.

Each seal may be in the form of a slit tube of ductile metal having a slit along its length, the spring extending along the interior of the slit tube to be embraced thereby, and the slit tube providing a pair of sealing flanges on opposite sides of the spring 0 5which form said sealing strips, the spring forming a radially 0 0 resilient core for the slit tube and the slit in the wall of the slit tube facilitating deformation thereof.

One of the electrode compartments will be an anode 10 compartment, the other being a cathode compartment. Typically the active anode substance comprises a molten alkali metal such as sodium, the liquid electrolyte also being molten, comprising eg an alkali metal aluminium halide. In this case there is a movement of anode substance ions such as sodium ions through the separator from the anode compartment into the cathode compartment during discharaing, and, upon charging, a movement of said ions in the opposite direction through the separator, gas spaces being provided above the liquid levels in the compartments.

In a particular embodiment of the cell the anode is inolten sodium and the cathode is in the form of an electronically conductive electrolyte -permeable matrix impregnated with liquid electrolyte, the liquid electrolyte being sodium aluminium halide (eg chloride) molten 0 salt electrolyte and the separator being a solid conductor of sodiun, ions such as beta alumina or nasicon, or a micromolecular sieve which contains sodium sorbed therein. In this embodiment the matrix may be formed from at least one member of the group comprising Fe, Ni, Co, Cr 0 and Nin and compounds of one or more of said transition metals with at least one non-metal of the group comprising carbon, silicon, boron, nitrogen and phosphorous.

With regard to the solid conductor of sodium ion's or micromolecular sieve, this separates the anode compartment from the cathode compartment so that any active anode substance such as sodium moving from the anode to the electrolyte, or vice versa, has to pass through the internal crystal structure of the solid conductor or through the microporous interior of the micromolecular sieve, as the case may be, passing in atomic form through the interface between the 1 1 anode and separator and passing in ionic form through the interface between the electrolyte and separator.

By lhicromolecular sieve" is meant a molecular sieve havina interconnected cavities and/or channels in its interior and windows and/or pores in its surface leading to said cavities and channels the windows, pores, cavities and/or channels having a size of not more than 50 Angstrom units and preferably less than 20 Angstrom units. Such sieves include mineral micromolecular sieves such as the 10 tectosilLcates, examples of which are zeolites 13X, 3A and 4A.

1 In a particular embodiment of the invention, the separator may be in the form, of a separator tube which is closed at one end thereof and open at the other, the cell housing comprisinog a cylindrical casing arranged concentrically around the separator tube and spaced therefrom, a said compression seal between the separator tube and the housing being provided at the open end of the separator tube via an insulating ring of electronically insulating material, the open end of the separator tube being hermetically glass-welded to the ring and the compression seal. being between the.1.iisLilRti nc, ring and the casing, and the open end of the separator tube being provided with a sealed closure forming part of the housing, so that the separator tube divides the interior of the housing into said pair of electrode compartments, one of which is in the interior of the separator tube and the other of which is between the separator tube and the casing.

The cell may comprise two said compression seals, namely said compression seal between the insulating ring and the casing and a C1 compression seal between the insulating ring and the sealed closure of the separator tube, the insulating ring having a pair of oppositely 0 axially facing end faces against which the compression seals abut and C 0 the seals being stressed by a force acting in said axial direction.

0 Each compression seal may be annular in shape so that it functions as an 0-ring seal, the ductile metal of the seal being in the form of an endless ring-shaped hollow toroid, the coil sprincr 0 extending along the full length of the interior of the toroid. As 0 indicated above, the toroid may have a slit along its length to 0 1 facilitate plastic deformation thereof, and this may be at its outer periphery relative to its polar axis.

-Bearing the aforegoing in mind, a particularly preferred embodiment of the cell may be one in which the anode material is sodium located between the separator tube and the casing, the active cathode material being, in the fully charged state of -the cell, MC1 2 where M is a transition metal selected from the group comprising Fe, NI, Co, Cr and Hi or mi,-ctures thereof, and being located in the interior of the separator tube together with the electrolyte which is, in the fully charged state of the cell, sodium aluminium chloride 0 according to the formula Na.A.1C1 in which the molar ratio of Na:A1 is 0 4 not less than 1, the active cathode material being dispersed in an electrolyte-permeable electronically conductive porous matrix impregnated with the electrolyte, the insulating ring being of 0 alpha-alumina, and the separator tube being of beta"-alumina.

The metal of the seals should be inert in the cell environment of the cell compartment which it seals. The metal should thus not react elither chemnically of eLectrochc,-,i-teail..ILY during c,- .L.L operation with the active electrode substance or electrolyte of the cell compartment which it seals.

Thus, where M is selected from Fe, Ni or mixtures thereof, each compression seal may be of nickel or a nickel alloy which is inert in the cell environment to the contents of the electrode compartments.

The molar proportion of alkali metal cations in the electrolyte is preferably, as indicated above, at all stages of charge of the cell, no less than the molar proportion of aluminium cations therein. When the electrolyte is a sodium aluminium chloride, this can be ensured by loading the cathode compartment -with sufficient sodium chloride, so that solid sodium chloride is present and in contact with the liquid electrolyte during all stages of charge. This sodium chloride in solid form should be present at least in all states of discharge, other than the fully charged state of the cell.

C) 1 The invention extends to a cell housing f or an electrochemical power storage cell which is divided by a solid separator into a pair of electrode compartments, one of which is an anode compartment for containing an active anode substance, and the other of which j s a cathode compartment for containing an active cathode substance and an electrolyte, the separator separating the anode compartment from the cathode compartment and being capable in use of permitting an anode substance to pass from the anode compartment into the cathode compartment and vice versa in ionic form, the separator being compression sealed to the housing to separate the compartments from each other, by at least one compression seal comprising, in combination, a close-wound radially resilient helical metal spring and at least one sealing strip of ductile metal, the spring providing a backing for each sealing strip and being stressable 0 C7 in its radial direction by a force sufficient resiliently to compress the spring in its radial direction and sufficient to cause plastic 0 deformation of each sealing strip.

0 The invention extends further, in a rechargeable high 20 tei.,ipe-ra'iure electrochernical powsr s-tv-rage cell co,,,i-,ris4Ln7 a cc!! housing divided by a solid separator into a p25r of ele---Lrode compartments, one of which is an anode compartment which contains an active anode substance, and the other of which is a cathode compartment which contains an active cathode substance and an electrolyte, said anode substance and said electrolyte being liquid at 0 the operating temperature of the cell, the separator separating the c> 0 anode substance from the electrolyte and cathode substance and permitting the anode substance in use to pass from the anode compartment into the cathode compartment and vice versa in ionic form, to a method of sealing the separator to the housing to separate the compartments from each other which comprises locating between the separator and the housing a compression seal comprising, in combination, a close-wound Tadially resilient helical metal spring and at least one sealing strip of ductile metal, the spring and each strip being located side-by-side so that the spring forms a backing for each strip, and urging the separator towards the housing to grip the spring and each strip therebetween with sufficient force to stress the spring into a state of resilient radial compression and to cause plastic deformation of each sealing strip.

0 The invention will now be described, by way of example, with 5 reference to the accompanying diagrammatic drawings in which:

Figure 1 shows a sectional side elevation of the housing of a high temperature rechargeable electrochemical cell in accordance with the present invention; Figure 2 shows a sectional side elevation of the seals of the 10 cell of Figure 1; Figure 3 shows a view similar to Figure 1 of a further embodiment of a cell according to the invention; and Figures 4A-4C show details of variations of the sealing arrangement of Figure 3.

In Figure 1 of the drawings, the cell housing is generally 0 C> designated by reference numeral 10 and is shown broken midway alone, t z> its length, typically having an outside diameter of about 50-60 mn, and a lenath of about 30-60 cm. The housina shown is for a cell having a 0 0 sodi,--q anode material. a sodi-LLm aluminivirn chinride liquid electrolyte and an cathode substance which in its charged state 0 comprises an electronically conductive active electrolyte -permeable porous matrix containing FeCl NiCl or FeCl,/NIC1 dispersed therein 2 and saturated with said electrolyte, the matrix having sufficient finely divided NaCl dispersed therein to ensure that, in all states of charge of the cathode substance, the electrolyte is an equimolar mix of NaCl and A1Cl-)3 ie stoichiometrically exact Na-klCl 4 The cell housing 10 comprises a mild steel outer casing 12 having a base 13 for supporting it in an operative upright attitude on a horiiontal support surface (not shoi.,n).- The Sasing 12 comprises a cylindrical can 12.1 and a mild steel casing seat 14 welded together at 15 at the top of the can 12.1. The seat 14 is closed off by an annular stainless steel or alintinium top casing or cap 16 welded thereto. The cap 16 has a stainless steel or aluminium, as the case may be, cell terminal post 18 welded thereto. An open-ended beta"-alumina separator tube 20 is located concentrically within the.

casing 12, the upper open end of the tube 20 being glass welded to an alpha alumina ring 22 which ring seats with a sliding fit at 24 against an inner curved surface provided thereforon the seat 14. The tube 20 is closed-ended at its lower end.

The tube 20 is closed-off by a mild steel closure member 26. 5 This closure member 26 clamps the alpha-alumina ring 22 against a shoulder 28 on the seat 14 and the closure member 26 is in turn clamped in position by the cap 16. The closure member 26 has a central passage 30 therethrough, within which is welded a stainless steel or aluminium terminal post 32. The lower end of the post 32 projects to a position adjacent the closed end of the tube 20 and has a nickel mesh 34 wrapped tightly around its outer surface.

0 The interior of the tube 20 forms a cathode compartment and is filled with molten salt electrolyte 36, there being a porous cathode matrix 38 formed on the outer surface of the terminal post 32 which post acts as a cathode current collector, the mesh 34 being embedded in the niatrLx 38. The space between the casing 12 and tube 20 is an anode compartment and contains molten sodium 40. Gas spaces 41, 42 (not to scale) are shawn above the electrolyte 36 and scdjum 40 20.especz-ve^, 1 ly.

The member 26 is sealed to the ring 22 by a nickel C 0-ring-type seal 44 located in a circ=erential groove 46 in the lower face of the member 26 and the ring 22 is in turn sealed to the 1 0 seat 14 by a nickel 0-ring-type seal 48 located in a rebate defined by 0 an annular shoulder 50 in the seat 14 adjacent the shoulder Z8. The cap 16 is electronically insulated from the member 26 by an annular mica disc 52.. and the member 26 is electronically insulated frori the seat 14 by a mica ring 54. The nickel 0-ring 44 seats in the groove 0 t> 46 on the member 26 via an annular grafoil (graphite) disc 56 and on the ring 22 via an annular aluminium disc 58, the 0-ring 48 similarly, seating on the shoulder 50 via an annular grafoil disc 60 and on the 0 ring 22 via an annular aluminium disc 62. The grafoil and alLuninium discs are optional and can, if desired, be omitted.

The housina 10 is accordingly for a cell of the so-called 0 L inside-cathode type, so that the porous cathode matrix 38 is fomied on the outer surface cf the post 32, the mesh 34 being eiibedded in this matrix and the mesh 34 and post 32 acting as the cathode current collector. The casing 12 will in turn act as the anode current collector.

In Figure 2 the seals 44, 48 are shown in more detail. They are of nickel and are essentially identical, each comprising an outer split tube 64 of nickel which is toroidal in shape ahd which has a longitudinal slit 66 along its outer periphery. A close-wound helical nickel coil spring 68 is located in the interior of the tube 64, and extends along its length. The tube 64 provides a pair of ductile flanges 70, 72 via which the seal seals against the member 26 and ring 22 (seal 44), and against the ring 22 and seat 14 (seal 48). In practice the Applicant has found that nickel seals of this type available under the Trade Mark "Helicoflex Type W' from Vakumet Products (Proprietary) Limited, in South Africa, are suitable for this purpose.

Turning to Figure 3, the cell shown is similar to the cell of Figure 1 in many respects, and unless otherwise specified, the same parts 54M Figurc 3 are desj,-,,,at--d by t-AhC sw.= J'n Figure 1.. There are, however, a number of detail dif.Lerences between the cells of Figures 1 and 3, as set out hereunder.

Thus, instead of seating directly against the casing seat 14 as shown at 24 in Figure 1, the alumina ring 22 seats against the seat 14 via a doimward extension of the insulation ring 54. The closure member 26 clamps the ring 22 downwardly, not against a shoulder 28 as shown in Figure 1, but against the shoulder 50 via the seal 48, the gTafoil disc 60 between the seal 48 and shoulder 50 of Figure 1 being 3 0 omitted in Figure 3.

The terminal post 32 in turn is merely welded to the top of the closure member 26 and does not project into the tube 20. Instead, a filler pipe 74 passes downwardly through the closure member 26 to which it is welded, and has a sealable closure (not shown). A nickel current collector rod 76. welded to the pipe 74 at 78, passes downwardly in a central position into the tube 20, to a position near the closed end of the tube 20. The mesh 34 is omitted andY instead, the matrix 38 has nickel gauze 80 embedded in it. The gaU7e 80 is spread through the volume of the matrix and acts as a cathode current collector,, being in contact with the rod 76. A suitably mounted annular wick casing 82 is provided around the tube 20, closely spaced therefrom, for wicking molten sodium anode material over the outer surface of the tube 20. The anode space between the casing 82 and tube 20 is optionally filled with a suitable porous wicking material (not shown) for assisting in the wicking of sodium over the outer surface of the tube 20.

The molten salt electrolyte and sodium (36 and 40 in Figure 1) are not shown in Figure 3.

The groove 46 in Figure 1 is replaced by an annular shoulder 84 provided by a rebate in the member 26, which rebate receives the seal 44 in abutment with the shoulder 84. The grafoil disc 56 of Figure 1 is omitted and the seal 44 seats directly against the 1 0 shoulder 84. The gasket 58, instead of being of aluainum as in Figure 17 is of grafoil in Figure 3.

An advantage of the cell construction shown, in Figure 3 is its ease of assembly. The casing seat 14 containing the mica ring 54 1 is welded at 15 to the casing can 12.1 to which the base 13 and wick casing 82 have been welded, the seal 48, aluminium disc or gasket 62 and alpha-alumina ring 22 (to which the tube 20 has been previously welded by glass) are inserted in turn into position, followed by the grafoil disc or gasket 58 and closure member 26 (to which the terminal part 32 and pipe 74 have previously been welded, with the rod 76 and its gauze previously connected to the pipe 74). The mica disc S2 and cap 16 are then placed in turn in position. The top cap 16 is then loaded axially inwardly (downwardly in Figure 3) with sufficient force to provide the springs of the seals 44, 48 with the appropriate degree of resilient compression, and with sufficient force to cause flow of their ductile metal flanges 70, 721 (Figure 21). The top cap 16 (to which the teminal post 18 has previously been welded) is finally welded., with the seals 44, 48 under compression, to the casing seat 14 at 86.

To load the cell, a vacuum can be drawn in the anode space between the casing 12 and tube 20 via a suitable closable opening (not 0 shown) through the cas ing 12, and a suitable mixture of iron powder, 0 sodium chloride powder and sodium aluminium chloride powder can be charged into the interior of tube 20 via the pipe 74.

The cell can then be raised to its operating -temperature to weld the sodium aluminium chloride powder to form an electrolyte, and can be charged, the iron powder reacting with the sodium chloride to form FeCi 2 and sodium in ionic form passing through the tube 20 into the anode compartment between the tube 20 and casing 12, to form molten sodium anode material. A suitable starting mixture is charged into the tube 20 so that, after several charge/dis charge cycles the porous iron matrix 38 is automatically formed around the rod 716 and gauze 80, impregnated with molten liquid electrolyte and in the presence of a small amount of excess sodium chloride in all states of charge of the cell.

It is to be noted in particular that the seals 44, 4S are selected and' are cc-,rp-,--ssed during --sEciiibl.r en all temperatures to which the cell is expected to be exposed, in particular from ambient teraperature up to the cell operating 0 temperature, the coil springs 68 are resiliently compressed and not plastically deformed, and so that the flanges 70 (Figure 2) are plastically deformed. In this way, reliable effective sealing is promoted, and in tests conducted by the Applicant on prototype cells, as shown in Figure 3, cell sealing failures at the seals 441, 48 have 0 oc cur red at a rate of less than 1%.

Further advantages include low cost of seals which are commercially available, and automatic easy alignment of the tube 20 centrally in the casing 12.

Turning now to Figures 4A. to 4C, variations are shown of the C) sealing arrangement of Figure 3, and unless otherwise specified the 0 0 same reference numerals are used for the same parts in Figures 4A to 4C, as aye used in Figure 3. In Figures 4A to 4C a detail is shown 1 corresponding to the top right hand corner of Fi gure 3, and in each case the detail is generally designated 86.

In Figure 4A the seal 44 is shown replaced by an annular knife-edge type seal 88, spaced radially inwardly adjacent the outer periphery of the lower surface of the closure member 26, with which it is fast. and extending circumferenti ally alongside said periphery. The knife-edge of this seal seals doisnwardly axially against the axially upwardly facing surface of the alpha-alumina ring 22, via the grafoil gasket 58 as shown.

In the case of Figure 4B the seal 44 is retained, and it is instead the seal 48 which is replaced by an annular knife-edge type seal, in this case designated 90. This seal 90 is fast with and extends circumferentially along the radially inner peripher of the shoulder 50 of the seat 14. Its kmife edge seals axially upwardly aaajnst the axially downwardly facing surface of the ring 22, 0 c) 0 via the annular alumina disc 62 as shown.

Finally, in Fig re 4C both the seals 4,1,4A 2re replaced, Clu respectively by seals 8S and 90 of the type shown respectively in Figures 4A and 4B. In Figure 4C a seal 92 oli the same type as the seals 44 and 48 and of the construction shown in Figure 2, is provided between the upper axially upwardly facing surface of the closure member 26 and the lower axially downwardly facing surface of the mica. disc 52, extending circumferentially along their outer peripheries and spaced radially inwardly adjacent said peripheries.

1

Claims

Claims:

1. A rechargedble high temperature electrochemical power storage cell which comprises a cell housing divided by a solid separator into a pair of electrode compartments, one of which is an anode compartment which contains an active anode substance, and the other of which is a cathode compartment which contains an active cathode substance and an electrolyte, said anode substance and said electrolyte being liquid at the operating temperature of the cell, the separator separating the anode substance from the electrolyte and cathode substance and permitting the anode substance in use to pass from the anode compartment into the cathode compartment and vice versa in ionic form,, the separator being compression sealed to the housing to separate the compartments from each other, by at least one compression seal comprising, in combination, a close-wound radially resilient helical metal spring and at least one sealing strip of ductile metal, the spring providing a backing for each sealing strip and being stressed in its radial direction by a force sufficient resiliently to compress the spring in its radial direction and sufficient to-cause plastic deformation of each sealing strip.

2. A cell as claimed in Claim 1, in which there are two said sealing strips on opposite sides respectively of each coil spring and plastically deformed thereby.

3. A cell as claimed in Claim 2, in which each seal is in the form of a slit tube of ductile metal having a slit along its length, the spring extending along the interior of the slit tube to be embraced thereby, and the slit tube providing a pair of sealing flanges on opposite sides of the spring which form said sealing strips, the spring forming a radially resilient core for the slit tube and the slit in the wall of the slit tube facilitating deformation thereof.

4. A cell as claimed in any one of Claims 1 to 3 inclusive, in which the separator is in the form of a separator tube which is closed at one end thereof and open at the other, the cell housing comprising a cylindrical casing arranged concentrically around the separator tube 1 I,l -13and spaced therefrom, a said compression seal between the separator tube and the housing being provided at the open end of the separator tube via an insulating ring of electronically insulating material, the open end of the separator tube being hermetically glass-welded to the insulating ring and the compression seal being between the insulating ring and the casing, and the open end of the separator tube being provided with a sealed closure forming part of the housing, so that the separator tube divides the interior of the housing into said pair of electrode compartments, one of which is in the interior of the 10 separator tube and the other of which is between the separator tube and the casing.

5. A cell as claimed in Claim 4, which comprises two said compression seals, namely said compression seal between the insulating is ring and the casing and a compression seal between the insulating ring and the sealed closure of the separator tube, the insulating ring cl having a pair of opposizely axially facing end faces against which the 0 compression seals abut and the seals being stressed by a force acting in said axial direction.

6. A cell as claimed in Clalm 4 or Cla.4m 5, J11-1 ench compression seal is annular in shape so that it functions as an 0-ring seal, the ductile metal tube of the seal being in the fom of an endless ring-shaped hollow toroid, the coil spring extending along the full length of the interior of the toroid.

7. A cell as claimed in any one of Claims 4 to 6 inclusive, in which the anode material is sodium located between the separator tube and the casing, the active cathode material is, in the fully charged state of the cell, NIC1 2 where M is a transition metal selected from the group comprising Fe, Ni, Co, Cr and Nhi or mixtures thereof, and is located in the interior of the separator tube together with the electrolyte which is, in the fully charged state of the cell, sodium aluminium chloride according to the-formula NaAlCl 4 in which the molar ratio of Na:Al is not less than 1, the active cathode material being dispersed in an electrolyte-permeable electronically conductive porous matrix impregnated with the electrolyte, the insulating ring being of alpha-alumina, and the separator tube being of beta-zilur.iina.

4 1

8. A cell as claimed in Claim 7, in which M is selected from Fe, Ni or mixtures thereof, each compression seal being of nickel or a nickel alloy which is Inert in the cell environment to the contents of the electrode compartments.

9. A cell housing for an electrochemical power storage cell which housing is divided by a solid separator into a pair of electrode compartments, one of which is an anode compartment for containing an active anode substance, and the other of which is a cathode corapartment for containing an active cathode substance and an electrolyte, the separator separating the anode compartment from the cathode compartment and being capable in use of permitting an anode substance to pass from the anode compartment into the cathode compartment and vice versa in ionic foiin, the separator being compression sealed to the housing to separate the compartments from each other, by at least one compression seal comprising, in combination. a close-wound radially resilient helical metal spring and at least one sealing strip of ductile metal, the spring providing a backing for each sealing strip and being stressable in its radial direction by a force sufficient resili.ently to coikoress the spring in its radial direction and sufficient to cause plastic defonlation of each sealing strip.

10. In a rechargeable high temperature electrocherdcal power storage cell comprising a cell housing divided by a solid separator into a pair of electrode compartments, one of which is an anode compartment which contains an active anode substance, and the other of which is a cathode compartment which contains an active cathode substance and an electrolyte, said anode substance and said electrolyte being liquid at the operating tenTerature of the cell, the separator separating the anode substance from the electrolyte and cathode substance and permitting the anode substance in use to. pass from the anode compartment into the cathode compartment and vice versa in ionic form, a method of sealing the separator to the housing to separate the compartments from each other which comprises locating between the 0 separator and. the housing a coffpression seal comprising, in combination, a close-wound radially resilient helical metal spring and at least one sealing strip of ductile metal, the spring and each strip -1 41 1 c being located side-by-side so that the spring forms a backing for each strip, and urging the separator towards the housing to grip the spring and each strip therebetween with sufficient force to stress the spring into a state of resilient radial compression, and to cause plaszic 5 deformation of each sealing strip.

1

11. A rechargeable high temperature electrochemical power storage cell, substantially as described and as illustrated herein.

12. A cell housing for an electrochemical power storage cell, substantially as described and as illustrated herein.

13. A method as claimed in Claim 10, substantially as described herein.

Published 1988 at The Patent Office. State House, 6671 High Rolborri, London WC1R 4TP. Further copies may be obtained from The Patent office, Sales Brancli, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Cori. D87.